Rather than dumb sparrows, I interpret them to be the lesser brothers of the massive and improbable bird that hurtles downward from far above them. This creature, or construct, or abomination - this phenomenon of imagination - is composed of flesh made metal and metal made flesh, clockwork and feathers and bellows and lungs all heated to a sullen glow, a meteor shedding altitude for speed.
The sparrows chirp lightly in recognition as the fallen satellite hits the ground just before unfurling it's wings - it is here that the listener realizes that this bird is meant to fly in thicker skies than those we know. The deepest troughs of our atmosphere are hard and featureless vacuum to this thing. It flies instead under the surface of the Earth, skipping and gliding along the thermals of the mantle, spinning and diving through magma and diamond alike, then climbing from time to time to broach the enamel-thin surface of our world. It erupts from below in gouts of pulverized granite and feldspar, basking in near-silence before plunging back into the crust.
But then, around 3:45 in the playback, something goes dreadfully wrong. Whether the earthbird is damaged or ill is unknown. But the rhythm of its wings is altered, and not for the better. Was it shot by some wary guardsman as it toyed with the surface world? Are there predators lurking in the stony fathoms below? Or was this no more than the aging of a plaything put to use more rigorous than it could sustain? No matter, for now there is a battle afoot.
The battle is fought heartbeat by stuttering heartbeat, the bird swooping core-ward and back, perhaps seeking to fuse its broken parts in the heat of Earth's molten womb. But the mending is imperfect. And now the crippled beast must fight more furiously through the crushing strata.
Fight it does. And though the song ends, the listener knows that this combat will continue until the core grinds to a halt, solidifying in the final inevitable chill.